Spot frequency oscillator system



.Jam 4, 1949.

G. F.1MoYNAHAN, JR l 2; ASPOT FREQUENCY'-OSCIILLAIOR SYSTEM Filed Marcn'auls* I SPOT-FREQUENCY sTABlLlzvER Patented Jan. 4, 1949 imitan fsm.

Eis

marily to"fcreepage' of the local oscillator frequency during changes in ambient temperature, particularly during vthe warm-up period,h changes in line voltage, etc. Forimprcving stability auto,-4 matic frequencyl control methods can beulusedfor crystals can .be incorporated inthe circuit at certain spot frequencies. These expedients can-f. not, "however, be appliedto an existing .receiver without considerable rebuilding, o

It isa principal .object of .my invention to pro; vide novel andsimple means whereby-a continu-r1 ously tunable ,oscillator .can `be rendered" stable-.at selected fspo't frequencies. u

It .is a further object of my inventiontopm-` videa stabilizing circuit for an oscillator, suc n) the .local oscillator of. a superheterodyne .ref :feiver,A which canV be .readily attached 'with a I rninixrronn of alteration-of the existing-circuit. q

In 'accordance with my i` ention an auxiliarjyy crystalf-,controlled oscillator circuit, having Sel/T1 eral selectable crystals, is interconnectedfatfv-a point in Ytheilexisting oscillator of the receiver. i Switch, means is provided in theA au-xiliarycirc it wherebyin one .,positionof theswitch the .existing oscillator functions normally. A tother positions, the I auxiliary oscillator, vfunctions to operateat `|a desired spot-frequenoyor a subharmonc thereof., andthe existing oscillator circuitis reconstituted either as a buffer amplier, if the crystaloperates at. the fundamental frequency oras a frequencyv multiplien-if the crystaloperateslat a sub,-V harmonic. Y i

For 'a better understanding.v of, the'v invention together with other and -furtherobjects thereQi,

reference is vhad tothe'fo1lowing description, i

taken -in,.0r1.neti0n with. the. accompanying. drawing whichshows, -a schematic, circuit iof the invention.

. In `the o rawing, the portion of? the circuit-shownwithin `the dot-dash-;enclosureI `8 represents a standardoscillator-circuit suchlas is used as the local oscillatorjof a conventionalsuperheterodyne receiver. This oscillatorcomprises avtriole H)V 0911116075611 `t0;--,'iz.t '=\1`1l .Circuit IZ, including a 6.0.11.- tinucuslv variable tuning. lldllsllfl. andea l l 2 @Pred @il Mt11911111@til` inthe plate @ed arid circuits to provide feedback; Condensers fland Zuserve asfseriesand 'allelpadd lxidensers, '@middenZ2-aandient@#were cpnlcnsr and feidfieek.- The nadie breken andl connected to.. one Section Senior. Sie@ teria @urbes ,foibe after. Injection of losci ions mid-libel@ .et bf .Supeheterodvne receiver .is accomplish dI rby a. :connection ,from the 4cathode of tube l0 to the mixer cathode.

The remainder of the circuit, i. e., the elements outside ,theY dotedash enclosure 8, constitutes the Speiefrequenwtabilieer. which :the main fea: ture of Illy-invention." `It 1ser-ves to stabilize the tuning. O f @clonal eseillatewt..selected points of the. tuning :range Of-fondenser 4.4@ "li-liefste,- bilizerfmavbe-builtas a. Separatunit or incorporatedas anintegral'part of .the receiver.

The; stabilizer'. is a crystal-controlledV oscillator circuit of the Pierce type, and includes 'a tube `3l! having aresistor 38 :between its .gridand` cathode, and @load resistor@ rin iitsplate circuit..

Between@ endrancplatecf when ,is adapt- 1 @Meh internes@ one-efeplulfaliivofCrystals 32x-3.6, ,unedfiondi reetffresluencies, byfmeans l @Chien lffthe :threevscctien Switch fof, .theOthell-WQ-Secioiisare labelled. Staand 10.2.- @1 tleseiierii being uhnlrelledf as indi.- caterY .by t e brolen line.` Switch-.section Ellis interposedj in .the 1connection between .the .grids W1 1.1 bheSWitChes intresten.. I. all -rystels 32.-. ei-.@idiscolfineied whe39end-pedder den? More.disoneededend the end. of mbe l0 liso onnected t0, theV tanll circuit `I.2,A whereby 12h? Cir f flllliln in is'lrmel .meneer ias the veakoscillater ef.. ,the receiver..

'With the swwhseciilens. in any @i .positions 271-6 heA of .tube itl .is ,disconnected from ythe tan. @Circuit `bv Switch section 10., whereby it ceases .toyosoillate. The switch alsoconnectsgthe allilrvf Paddel @Gedener :49, i @MOSS the., tank. circuit to compensate for the reinoval. f the tube and .lead capacities. 1f11om,the ci. .musothat the tankirsuitalibration is notdsturbed, whereby ifwllzstillftreek with:the.tunedfredieffrequenv circuits for the receiven4 -Switoh sectienfl] con-,- S1011. ofltghefcrystalslzr betweenlthefplate tuhellmherebyfi begins tooscillat ...tedclwstaltfrequencn kEi.r.i.a.11.y,.switch plier or harmonic amplifier or generator tuned to l the desired harmonic which constitutes the spot frequency.

When the oscillator 8 is functioning normally, i. e., when the spot-frequency circuit and its crystals are disconnected, there still may be a tendency to lock-in when the oscillator is tuned near the crystal frequency due to capacitative coupling between the oscillator circuit and the crystal. This can be avoided by shielding the switch units or by adding a switch section which will ground the crystals when not in use.

While there has been described what is at present considered a preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

1. The method of stabilizing an electron tube oscillator, having a load circuit which vis tunable over a predetermined frequency range, at at least one frequency within said range, comprising the steps of altering the -circuit of said oscillator to function as a radio-frequency amplifier tuned by said load circuit, tuning said load circuit to said one frequency, and impressing stable oscillations upon said amplifier, said one frequency having a harmonic relation to said stable oscillations.

2. In the operation of a superheterodyne receiver including a local electron tube oscillator having a load circuit which is continuously tunable over a predetermined frequency range, the method of stabilizing the tuning of said local oscillator of one frequency at said range, comprising the steps of altering the circuit of said oscillator to function as a radio-frequency amplifier tuned by said load circuit, tuning said load circuit to said one frequency, and impressing stable oscillations upon said amplifier, the frequency of said oscillations being equal to said one frequency.

3. In the operation of a superheterodyne receiver including a local electron tube oscillator having a frequency determining circuit which is continuously tunable over a predetermined frequency range, the method of stabilizing the tuning of said local oscillator at one frequency of said range, comprising the steps of altering the circuit of said oscillator to function as a harmonic generator tuned by said circuit, tuning said circuit to said one frequency, and impressing crystalcontrolled oscillations upon said generator to stabilize it at said one frequency, the frequency of said oscillations being equal to a subharmonic of said one frequency.

4. An oscillator network comprising first and second electron tubes, a continuously-tunable circuit for said iirst tube, means to connect a utilization circuit to said iirst tube, a stable, fixed resonating means connected to said second tube, and selective means to either render said first tube'oscillating and disable said second tube or to cause said second tube `to generate oscillations which are impressed upon said first tube.

5. An oscillator network comprising iirst and second electron tubes, a continuously-tunable circuit for said first tube, a utilization circuit coupled to said tunable circuit, at least one stable reson'ating means connected to said second tube and tuned to a subharmonic of one frequency Within the range of said tunable circuit, and switch means so connected in said network that, in one position, it causes said iirst tube to oscillate and disables said second tube, and, in another position, it causes said second tube to generate oscillations and reconnects said iirst tube so that it functions as a harmonic generator controlled by said oscillations.

6. A local oscillator network for a superheterodyne receiver comprising first and second electron tubes, a continuously-tunable circuit, means adapted to couple the input and output circuits of said first tube to said tunable circuit in feedback relation, a plurality of piezoelectric crystals adapted to be selectively connected to said second tube to cause it to oscillate at the frequency of one of said crystals, and a multipleposition switch so connected in said network that, in one position, it renders said first tube oscillating and disables said second tube, and, in any other position, it connects one of said crystals to said second tube to cause it to oscillate at the crystal frequency, disables the feedback relation of said first tube, and connects the grid of said first tube to the output circuit of said second tube, whereby said iirst tube acts as a buier amplifier tuned by said tunable circuit. v

7. A local oscillator network for a superheterodyne receiver comprising first and second gridcontrolled electron tubes, a continuously-tunable circuit, a utilization circuit coupledvto said tunablecircuit, means adapted to couple the grid and plate circuits of said iirst tube to said tunable circuit in feedback relation, a plurality of piezoelectric crystals adapted to be selectively connected to said second tube to cause it to oscillate at the frequency of one of said crystals, a multiple-position switch so connected in said network that, in one position, it renders said first tube oscillating and disconnects said second tube and said crystals, and, in any other position, it connects one of said crystals to said second tube to cause it to oscillate at the crystal frequency, disconnects the grid of said first tube from said tunable circuit and connects it to an oscillation circuit of said second tube, whereby said first tube acts as a buffer amplifier, and a reactance adapted to be connected to said tunable circuit by said switch in said other position to compensate for changes in the effect of interelectrode capacity of said first tube.

8. A local oscillator network for a superheterodyne receiver comprising first and second gridcontrolled electron tubes, a continuously-tunable circuit, a utilization circuit coupled to said tunable circuit, means adapted to couple the grid and plate circuits of said first tube to said tunable circuit in feedback relation, a plurality of piezoelectric crystals respectively tuned to a subharmonic of a different frequency within the range of said tunable circuit and adapted to be selectively connected to said second tube to cause it to oscillate at the frequency of one of said crystals, a multiple-position switch so connected in said network that, in one position, it renders saidV iirst tube oscillating and disconnects said second tube and said crystals, and, in any other 5 6 position, it connects one of said crystals to said REFERENCES CITED second tube to cause it to generate oscillations at the crystal frequency, disconnects the grid of said rst tube from said. tunable circuit and The following references are of record in the file of this patent:

connects it to an oscillation circuit of said sec- 5 UNITED STATES PATENTS ond tube, whereby said rst tube acts as a har- Number Name Date monic amplifier controlled by said oscillations, 2,114,113 Egberts 111111,12, 1933 and a capacity adapted to be connected across 2,323,956 Yerian Ju1y 13y 1943 to said tunable circuit by said switch in said other 2,338,366 Muniz eta] Jam 11, 194,4t position to compensate for changes in the effect 10 2,401,481 Harriett June 4, 1946 of interelectrode capacity of said first tube. 2,414,795 Brandt Jan. 28, 1947 GEORGE F. MOYNAHAN, JR. 2,439,844 Davis Apr. 20, 1948 

